<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <ul>
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
        <li>6</li>
        <li>7</li>
        <li>8</li>
        <li>9</li>
        <li>10</li>
    </ul>
</body>
</html>
<script>
    // var lis=document.getElementsByTagName("li")
    var lis=document.querySelectorAll("li")
    var li=document.querySelector('#first')
    var second=document.querySelector('.second')
    // console.log(lis);
    for(var i in lis){
        console.log(lis[i]);
    }
    for(var i=0;i<lis.length;i++){
        console.log(lis[i]);
    }
</script>